/// <summary>
/// 入力データが完全に復元できる特殊な窓関数を使用したオーバーラップ・アドFFT。
/// あらかじめSetNumSamples()を呼ぶと入出力サンプル数が一致する。
/// </summary>
/// <param name="fftLength">Forward FFT長。</param>
/// <param name="ifftLength">Inverse FFT長。0のときForward FFT長を使用。</param>
public WWOverlappedFft(int fftLength, int ifftLength = 0)
{
mFFTfwd = new WWTimeDependentForwardFourierTransform(fftLength, WWTimeDependentForwardFourierTransform.WindowType.Hann);
if (ifftLength == 0)
{
ifftLength = fftLength;
}
mFFTinv = new WWTimeDependentInverseFourierTransform(ifftLength);
}
public void TimeDependentFourierTransformTestImpulse()
{
var t = new WWTimeDependentForwardFourierTransform(4, WWTimeDependentForwardFourierTransform.WindowType.Bartlett);
var f = new WWTimeDependentInverseFourierTransform(4);
var x = new double[20];
x[0] = 1;
Test(t, f, x, 1);
}
public void TimeDependentFourierTransformTestDClong()
{
var t = new WWTimeDependentForwardFourierTransform(4, WWTimeDependentForwardFourierTransform.WindowType.Bartlett);
var f = new WWTimeDependentInverseFourierTransform(4);
var x = new double[20];
for (int i = 0; i < x.Length; ++i)
{
x[i] = 1;
}
Test(t, f, x, x.Length);
}
public void TimeDependentFourierTransformTestSine()
{
var t = new WWTimeDependentForwardFourierTransform(4, WWTimeDependentForwardFourierTransform.WindowType.Bartlett);
var f = new WWTimeDependentInverseFourierTransform(4);
var x = new double[20];
for (int i = 0; i < x.Length; ++i)
{
x[0] = Math.Sin(i * 2.0 * Math.PI / x.Length);
}
Test(t, f, x, 1);
}
public void TimeDependentFourierTransformTestHannDC()
{
var t = new WWTimeDependentForwardFourierTransform(8, WWTimeDependentForwardFourierTransform.WindowType.Hann);
var f = new WWTimeDependentInverseFourierTransform(8);
var x = new double[19];
for (int i = 0; i < x.Length; ++i)
{
x[i] = 1;
}
f.SetNumSamples(x.Length);
Test(t, f, x, 1);
}
//
//You can use the following additional attributes as you write your tests:
//
//Use ClassInitialize to run code before running the first test in the class
//[ClassInitialize()]
//public static void MyClassInitialize(TestContext testContext)
//{
//}
//
//Use ClassCleanup to run code after all tests in a class have run
//[ClassCleanup()]
//public static void MyClassCleanup()
//{
//}
//
//Use TestInitialize to run code before running each test
//[TestInitialize()]
//public void MyTestInitialize()
//{
//}
//
//Use TestCleanup to run code after each test has run
//[TestCleanup()]
//public void MyTestCleanup()
//{
//}
//
#endregion
private void Test(WWTimeDependentForwardFourierTransform t, WWTimeDependentInverseFourierTransform f, double [] x, int fragmentSize)
{
int iPos = 0;
int oPos = 0;
// Processのテスト。
while (iPos < x.Length)
{
int size = fragmentSize;
if (x.Length - iPos < size)
{
size = x.Length - iPos;
}
var xF = new double[size];
Array.Copy(x, iPos, xF, 0, size);
iPos += size;
var X = t.Process(xF);
if (0 < X.Length)
{
var xR = f.Process(X);
if (0 <= xR.Length)
{
for (int j = 0; j < xR.Length; ++j)
{
Assert.IsTrue(Math.Abs(xR[j] - x[oPos]) < 1e-8);
++oPos;
}
}
}
}
{
// Drainのテスト。
var X = t.Drain();
var xR = f.Process(X);
for (int j = 0; j < xR.Length; ++j)
{
if (x.Length <= oPos)
{
break;
}
Assert.IsTrue(Math.Abs(xR[j] - x[oPos]) < 1e-8);
++oPos;
}
}
}
public override PcmFormat Setup(PcmFormat inputFormat)
{
mPcmFormat = new PcmFormat(inputFormat);
/* 周波数の精度 = メインローブの幅/2
* Bartlett窓やHann窓のとき 4π/M ラジアン、M == FFTsize
* 人間の耳は、超低音域の音程は長3音(=1.26倍)ずれていても気にならないという。
*/
mFftLength = Functions.NextPowerOf2(mPcmFormat.SampleRate);
mFFTfwd = new WWTimeDependentForwardFourierTransform(mFftLength,
WWTimeDependentForwardFourierTransform.WindowType.Hann);
mFFTinv = new WWTimeDependentInverseFourierTransform(mFftLength);
mTotalSamples = inputFormat.NumSamples;
mProcessedSamples = 0;
return(inputFormat);
}
